1. Field of the Invention
The present invention generally relates to surgical sutures, and more specifically relates to automated systems and methods for making braided barbed sutures.
2. Description of the Related Art
Surgical sutures are used to close wounds and surgical incisions, and to repair damaged muscles, vessels, and tissue. Typically, a needle is attached to one end of a surgical suture, and the needle is drawn through tissue to form one or more loops holding the tissue together. The suture is subsequently tied off in one or more knots so that the tissue will remain drawn together.
There have been a number of attempts directed to improving sutures. For example, U.S. Pat. No. 4,546,769 to Planck et al. discloses a suture including a jacket made of a tubular braided structure, such as non-crimped yarns, and a core located within the jacket containing crimped fibers. The jacket is formed by braiding the non-crimped yarns around the core, which provides a suture that is easier to bend, easier to handle, and that makes better knots.
Although sutures are very effective for closing wounds, there are a number of challenges associated with using conventional sutures. Many of these challenges are directly related to the knots used to secure sutures in place. If the knots are not tied properly, defects may arise including slippage, knot breakage, and re-opening of the wound. In addition, using knots to secure sutures may distort tissue, restrict blood flow, increase the formation of scars, impede wound healing, and result in infection.
In response to the above-noted deficiencies associated with conventional sutures, sutures having barbs have been developed. Unlike conventional sutures, barbed sutures have projecting barbs that allow the suture to be used to close wounds, approximate tissue, tighten tissue, and attach prosthetic devices without using knots. U.S. Pat. No. 5,931,855 discloses barbed sutures that are used for cosmetic procedures such as brow-lifts and face-lifts. Fixing conventional sutures with knots requires the knots to be pushed down toward the tissue to assure proper tensioning and fixation of the sutures. In contrast, barbed sutures achieve proper tensioning and fixation by applying tension to the suture.
One problem associated with barbed sutures is that the barbs may delaminate or separate from the core of the suture, which may lead to device failure. In response to problems encountered with barbed sutures, braided barbed sutures having more durable barbs have been developed. In one embodiment of commonly assigned U.S. Patent Application Publication No. 2007/0005110, the disclosure of which is hereby incorporated by reference herein, at least one barbed filamentary element is intertwined along its length with a plurality of unbarbed filamentary elements, and the plurality of barbs extend outwardly beyond the unbarbed filamentary elements. In one embodiment, a braided barbed suture made using the methods disclosed in the '110 publication had a 96% improvement in holding strength compared to a barbed monofilament. Thus, superior holding strength was achieved without requiring the use of knots.
Other efforts for making braided, barbed sutures include manually delivering a barbed filament into a winding filament assembly. This approach requires an operator to adhere to a complex series of steps including running a braider to form a first length of unbarbed suture, turning the braider off, positioning a barbed filament at the braider eyelet where the filaments wind together, then turning the braider back on and allowing the winding filaments to draw the barbed filament into the braid. This approach provides very little control over the twisting of the barbed filament as it is drawn into the braid, which often results in undesirable braiding quality. This approach is also extremely labor intensive because an operator is required to continually turn the braiding equipment on and off while adjusting the position of the barbed filament. In addition, the barbed insert material being braided is greatly affected by the winding filaments themselves or by the vibration created as a result of winding. The vibration generated by the braiding equipment can result in the barbed material whipping, twisting, getting caught in the filaments, or accumulating undesirable rotation.
In spite of the above advances, there remains a need for improved systems and methods for making braided, barbed sutures, including automated systems and methods for making braided, barbed sutures. There also remains a need for improved systems and methods that consistently produce braided barbed sutures meeting exacting standards, and that transform barbed inserts having barbs in a single plane into braided barbed sutures having barbs in multiple planes.